Recently, with miniaturization of electric devices, circuit substrates have been made thin. In order to package parts in a complicated and narrow space inside a small electric device (small portable device) in a high-density manner, flexible printed circuits (FPC) which can be bent have been used. Further, a technique, in which a circuit pattern is formed on a box body itself so as to realize a small body and a light weight, is proposed.
Under such condition, in a case where a typical semiconductor package, for example, a semiconductor package of a resin-sealing type represented by QFP (Quad Flat Package), BGA (Ball Grid Allay), and CSP (Chip Scale Package) is used in a small portable device in particular, there occurs the following problems.
That is, even though a thin substrate or a flexible printed substrate can be bent (transformed) so that its shape is complicated in the small portable device, it is impossible to bend a typical semiconductor package due to its hardness. This means that: a semiconductor device which cannot be transformed is provided on a flexible printed substrate which can be bent freely, so that it becomes difficult to mount the substrate in a space having a complicated shape inside the small portable device.
It is also difficult to mount a hard semiconductor package on a circuit formed on a curved surface of a box body.
In order to solve the problems, Japanese Unexamined Patent Publication No. 64379/1994 (Tokukaihei 6-64379)(Publication date: Mar. 8, 1994) and Japanese Unexamined Patent Publication No. 11129/2000 (Tokukai 2000-11129)(Publication date: Jan. 14, 2000), for example, recite such a technique that: a semiconductor device (hereinbelow referred to as semiconductor chip) is made thin so as to be flexible, thus bringing about no problem in bending.
Typically, flip chip bonding is performed upon electrically connecting a semiconductor chip to a circuit substrate so as to make a thickness of whole the semiconductor chip thin. This is based on the following reason. In a case where wire bonding is performed upon electrically connecting the semiconductor device to the circuit substrate, it is necessary to coat a wire with an epoxy resin etc. for protection, which causes the semiconductor package to be thick, so that it becomes difficult to bend the semiconductor package.
In a case where the semiconductor chip and the circuit substrate are connected to each other in accordance with the flip chip bonding for example, a protruding electrode formed on an externally-drawing electrode of the semiconductor chip is positioned corresponding to an electrode on the circuit substrate, and is pressed so that the protruding electrode and the electrode on the circuit substrate are in contact with each other, and an adhesive resin is cured. This enables the semiconductor chip to be packaged on the circuit substrate in accordance with the flip chip bonding, so that a thin semiconductor package is formed.
Note that, as to the foregoing publications, Japanese Unexamined Patent Publication No. 11129/2000 (Tokukai 2000-11129)(Publication date: Jan. 14, 2000) discloses an example in which a semiconductor chip is packaged on a circuit substrate via an anisotropic conductive sheet in accordance with the flip chip bonding.
Since a semiconductor package manufactured in this manner has an extremely thin semiconductor chip compared with a typical semiconductor package, it is possible to make the semiconductor package itself thin, so that the semiconductor package can be curved. Thus, it is possible to provide the semiconductor package on a curved surface of a narrow space in a box body etc.
Further, when a thickness of the semiconductor chip is set to be not more than 100 μm so as to make the semiconductor package thin, the semiconductor chip tends to be damaged. Thus, it is difficult to treat the semiconductor chip in transporting the semiconductor chip or in packaging the semiconductor chip in the circuit substrate, so that there occurs such a problem that the productivity is led to worse.
Then, the following technique is proposed: a thick reinforcing member is temporarily formed on a side of a rear surface of the semiconductor chip so as to perform the flip chip bonding, and the reinforcing member is removed after performing the flip chip bonding, so that it becomes easier to treat the semiconductor chip which tends to be damaged in making the semiconductor chip thin.
Incidentally, in a case where the semiconductor chip and the circuit substrate are connected to each other in accordance with the flip chip bonding, it is typically required to use a thermally curable adhesive, represented by ACF (anisotropic conductive adhesive film) and ACP (anisotropic conductive adhesive paste), which softens or flows at least upon performing the flip chip bonding.
However, in a case where the foregoing thin semiconductor chip is connected to the circuit substrate in accordance with the flip chip bonding using the foregoing adhesive, there occur the following problems.
In typical flip chip bonding, as shown in FIG. 7, a semiconductor chip 101 is temporarily subjected to a pressure via a thermally curable adhesive 107 such as ACF on a circuit substrate 105 so that electrodes of the semiconductor chip 101 and electrodes of the circuit substrate 105 are electrically connected to each other. Under this condition, a bonding collet 110 presses the semiconductor chip 101 against the circuit substrate 105.
Thus, when the bonding collet adds a pressure, that is, when the bonding is performed, the heated adhesive 107 softens or flows due to the heat so as to overflows from a space between the semiconductor chip 101 and the circuit substrate 105, so that the heated adhesive 107 is inclined to surround a side face of the semiconductor chip 101.
Thus, as shown in FIG. 7, in a case where the boding collet presses the semiconductor chip 101 directly, there is a possibility that the overflowing adhesive 107 adheres to the bonding collet 110.
Further, as shown in FIG. 8, in a case where there is provided a reinforcing member 108 on the semiconductor chip 101, the adhesive 107 does not adhere to the bonding collet 110 depending on a thickness of the reinforcing member 108, but there is a possibility that the adhesive 107 adheres to the reinforcing member 107.
That is, as shown in FIG. 7, in the case where the adhesive 107 reaches the bonding collet 110, the bonding collet 110 is stuck on the semiconductor chip 101, so that it is difficult to perform the flip chip bonding successively without any problem.
Further, as shown in FIG. 8, in the case where the adhesive 107 reaches the reinforcing member 108, it is difficult to remove the reinforcing member 108 after packaging the semiconductor chip 101 on the circuit substrate 105.
Thus, in a case of using an adhesive which softens or flows upon performing the flip chip bonding so as to connect the semiconductor chip to the circuit substrate, there occurs such a problem that the productivity of the semiconductor package is led to worse.
Further, as shown in FIG. 8, the method in which the reinforcing member is formed on the semiconductor chip requires (a) a step of adding the reinforcing member to the semiconductor chip and (b) a step of removing the reinforcing member from the semiconductor chip packaged on the circuit substrate, so that the number of steps required in manufacturing the semiconductor package is increased. This also brings about such a problem that the productivity of the semiconductor package is led to worse.